The margin of sheet material, such as cloth, is often folded back and sewn to form a hem. The material may be manually folded back by a workers operating a sewing machine stitching the hem. However, in a commercially environment the manual folding and aligning of material is time consuming and inexact, often resulting in uneven hems or hems of different widths.
Formers have been provided which enable an operator to fold back the margin through the movement of the material through the former. Typically, these formers have plates which form a channel which progressively inverts the margin as the material is moved through the channel towards the sewing machine. However, to obtain a uniform hem these formers still rely on the operator's skill and close attention in directing the cloth through the former and in maintaining proper alignment of the material throughout sewing.
Formers have also been provided which use jets of air to urge material into a duct of the former. The duct has a guide at one end which the edge of the material abuts to maintain its alignment. This type of former is shown in U.S. Pat. No. 3,595,187. However, oftentimes the air from these jets causes the margin of the material to flutter, thus causing the margin to become misaligned.
A pneumatic hem former has also been designed having a reciprocating support plate mounted upon a guide wall having a series of orifices therein. A series of air nozzles generate air streams along the bottom of the support wall and into the channels or orifices. Such a device is shown in U.S. Pat. No. 5,373,797, which was invented by the Applicant herein. However, it has been found that loose threads associated with the edge of the working material becomes entrained into the air streams and pulled into the orifices of the guide walls. This often results in the material being pulled back by the loose threads in a direction opposite to the direction of material movement during sewing. When such occurs, the material becomes misaligned and the resulting sewn hem also is misaligned.
It thus is seen that a need remains for a former for folding back the margin of a sheet of material in a more efficient and effective manner. It is to the provision of such that the present invention is primarily directed.